U.S. patent application number 13/877539 was filed with the patent office on 2013-08-22 for vehicle braking/driving force control system and vehicle braking/driving force control method.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is Etsuo Katsuyama. Invention is credited to Etsuo Katsuyama.
Application Number | 20130218388 13/877539 |
Document ID | / |
Family ID | 45063191 |
Filed Date | 2013-08-22 |
United States Patent
Application |
20130218388 |
Kind Code |
A1 |
Katsuyama; Etsuo |
August 22, 2013 |
VEHICLE BRAKING/DRIVING FORCE CONTROL SYSTEM AND VEHICLE
BRAKING/DRIVING FORCE CONTROL METHOD
Abstract
Braking/driving force control that includes: detecting a
driver's operating state for causing the vehicle to run; detecting
a vehicle body motional state while the vehicle is running;
computing a target longitudinal driving force for causing the
vehicle to run and motional state amounts for controlling a vehicle
body behavior on the basis of the detected operating state and
motional state; and computing driving or braking forces allocated
to the wheels so as to achieve the computed target longitudinal
driving force and target motional state amounts and that the
braking/driving force generating mechanism causes the wheels to
generate independently.
Inventors: |
Katsuyama; Etsuo;
(Susono-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Katsuyama; Etsuo |
Susono-shi |
|
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi, Aichi-ken
JP
|
Family ID: |
45063191 |
Appl. No.: |
13/877539 |
Filed: |
October 20, 2011 |
PCT Filed: |
October 20, 2011 |
PCT NO: |
PCT/IB11/02512 |
371 Date: |
April 3, 2013 |
Current U.S.
Class: |
701/22 |
Current CPC
Class: |
B60L 7/14 20130101; B60L
7/18 20130101; B60T 2270/303 20130101; Y02T 10/645 20130101; Y10S
903/93 20130101; B60L 2260/28 20130101; B60T 8/1769 20130101; B60L
2240/12 20130101; B60L 2240/423 20130101; Y02T 10/64 20130101; B60T
2270/302 20130101; B60T 2260/06 20130101; B60L 2240/24 20130101;
Y02T 10/7275 20130101; B60L 7/26 20130101; B60L 15/2009 20130101;
Y02T 10/72 20130101; Y02T 10/646 20130101; B60L 2240/14 20130101;
B60L 2250/26 20130101; B60L 2270/145 20130101; B60T 8/17555
20130101; Y02T 10/70 20130101; B60L 15/20 20130101; B60L 2220/14
20130101; Y02T 10/7005 20130101; B60L 50/51 20190201; Y10S 903/947
20130101; B60L 2220/44 20130101 |
Class at
Publication: |
701/22 |
International
Class: |
B60L 7/18 20060101
B60L007/18; B60L 15/20 20060101 B60L015/20 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 21, 2010 |
JP |
2010-236095 |
Claims
1-10. (canceled)
11. A vehicle braking/driving force control system comprising: a
braking/driving force generating mechanism that causes each wheel
of a vehicle to generate driving force or braking force
independently of one another; a suspension mechanism that couples
each of the wheels that are not supported by springs of the vehicle
to a vehicle body that is supported by the springs of the vehicle;
an operating state detecting unit configured to detect a driver's
operating state for causing the vehicle to run; a motional state
detecting unit configured to detect a motional state of the vehicle
body while the vehicle is running; a vehicle body behavior control
value computing unit configured to compute a target longitudinal
driving force for causing the vehicle to run on the basis of a
detected driver's operating state, and a plurality of target
motional state amounts for controlling behaviors of the vehicle
body which are a target roll moment, a target pitch moment, and a
target yaw moment on the basis of the detected driver's operating
state and a detected motional state; and a driving force allocation
computing unit configured to compute driving forces or braking
forces respectively allocated to the wheels so as to achieve a
computed target longitudinal driving force and a plurality of
computed target motional state amounts which are the target roll
moment, the target pitch moment, and the target yaw moment at the
same time and that the braking/driving force generating mechanism
causes the wheels to respectively generate independently of one
another.
12. The braking/driving force control system according to claim 11,
wherein the driving force allocation computing unit computes
driving forces or braking forces that the braking/driving force
generating mechanism causes the wheels to respectively generate
independently of one another on the basis of arrangement of the
wheels and suspension mechanisms of the vehicle using an allocation
geometrically determined so as to achieve the computed target
longitudinal driving force and the plurality of computed target
motional state amounts.
13. The braking/driving force control system according to claim 11,
further comprising: a gain computing unit that, when allocated and
computed driving forces exceeds a maximum driving force of the
braking/driving force generating mechanism or when the allocated
and computed braking forces exceeds a maximum braking force of the
braking/driving force generating mechanism, computes a gain by
which driving forces or braking forces for achieving the plurality
of computed target motional state amounts within the allocated and
computed driving forces or braking forces are reduced.
14. The braking/driving force control system according to claim 13,
wherein the gain computing unit computes the gain in such a manner
that values obtained by subtracting driving forces for achieving
the computed target longitudinal driving force within the allocated
and computed driving forces from the maximum driving force are
divided by the driving forces for achieving the plurality of target
motional state amounts or values obtained by subtracting braking
forces for achieving the computed target longitudinal driving force
within the allocated and computed braking forces from the maximum
braking force are divided by the braking forces for achieving the
plurality of target motional state amounts.
15. The braking/driving force control system according to claim 13,
wherein the maximum driving force and the maximum braking force are
determined on the basis of a ground contact state of the
wheels.
16. The braking/driving force control system according to claim 11,
wherein the braking/driving force generating mechanism includes
electric motors that are respectively assembled to the wheels of
the vehicle, the braking/driving force control system further
comprising a torque computing unit that computes driving torques or
braking torques respectively generated by the electric motors in
correspondence with the allocated and computed driving forces or
braking forces.
17. The braking/driving force control system according to claim 11,
wherein the braking/driving force generating mechanism causes left
and right front wheels and left and right rear wheels of the
vehicle to respectively generate driving forces or braking forces
independently of each other, the driving force allocation computing
unit computes driving forces or braking forces that are allocated
to the left and right front wheels and the left and right rear
wheels in order to achieve the computed target longitudinal driving
force and the plurality of computed target motional state amounts
and that the braking/driving force generating mechanism causes the
left and right front wheels and the left and right rear wheels to
respectively generate independently of each other.
18. The braking/driving force control system according to claim 11,
further comprising: an input unit to which the detected driver's
operating state and the detected motional state are input, wherein
the vehicle body behavior control value computing unit computes a
target longitudinal driving force for causing the vehicle to run
and a plurality of target motional state amounts for controlling
behaviors of the vehicle body on the basis of the driver's
operating state and the motional state that are input by the input
unit.
19. A braking/driving force control method for use in a vehicle
that includes a braking/driving force generating mechanism that
causes wheels of the vehicle to respectively generate driving
forces or braking forces independently of one another and a
suspension mechanism that couples each of the wheels that are not
supported by springs of the vehicle to a vehicle body that is
supported by the springs of the vehicle the method comprising the
steps of: detecting a driver's operating state for causing the
vehicle to run; detecting a motional state of the vehicle body
while the vehicle is running; computing a target longitudinal
driving force for causing the vehicle to run on the basis of a
detected driver's operating state, and a plurality of target
motional state amounts for controlling behaviors of the vehicle
body which are a target roll moment, a target pitch moment, and a
target yaw moment on the basis of the detected driver's operating
state and a detected motional state; and computing driving forces
or braking forces that are respectively allocated to the wheels so
as to achieve a computed target longitudinal driving force and a
plurality of computed target motional state amounts which are the
target roll moment, the target pitch moment, and the target yaw
moment at the same time and that the braking/driving force
generating mechanism causes the wheels to respectively generate
independently of one another.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a vehicle braking/driving force
control system and vehicle braking/driving force control method
that individually control driving force or braking force to be
generated by each wheel of the vehicle.
[0003] 2. Description of Related Art
[0004] In recent years, there has been developed a so-called
in-wheel motor-type vehicle as one mode of an electric vehicle. In
the in-wheel motor-type vehicle, an electric motor (motor) is
arranged inside or near each wheel, and each wheel is directly
driven by the electric motor. In the in-wheel motor-type vehicle,
electric motors provided respectively for wheels (drive wheels) are
individually subjected to rotation control, that is, the electric
motors are individually subjected to power running control or
regenerative control, to individually control driving torque or
braking torque applied to each drive wheel to thereby make it
possible to appropriately control the driving force and braking
force of the vehicle in response to a running condition.
[0005] Then, there has been suggested a control system that uses
the function of individually controlling driving torque or braking
torque applied to each driving wheel in this way to suppress a
change in the behaviors of a vehicle body. For example, Japanese
Patent Application Publication No. 2007-110836 (JP-A-2007-110836)
describes a vehicle braking/driving force control system that
applies different braking/driving forces to respective driving
wheels to control pitch moment and yaw moment generated about the
barycenter of the vehicle in order to suppress vibrations of the
vehicle in the vertical direction (pitch rate) resulting from the
pitch behavior that occurs when the vehicle runs over a step, or
the like, of a road surface and to stabilize the yaw behavior in
the yaw direction. In addition, JP-A-2007-110836 describes a
vehicle control system that independently controls braking/driving
force of each driving wheel to control the roll behavior of a
vehicle body. Furthermore, Japanese Patent Application Publication
No. 2006-109642 (JP-A-2006-109642) describes a vehicle
braking/driving force control system that individually controls the
braking/driving force of each wheel to control the bouncing
behavior of a vehicle body.
[0006] Incidentally, in the above control systems, the driving
force or braking force of each driving wheel is controlled to
control the behaviors of the vehicle body (sprung mass) arranged on
springs, that is, on suspension mechanisms utilizing suspension
reaction force generated by the suspension mechanisms. However, the
above control systems each control only a single behavior, that is,
a pitch behavior, a yaw behavior, a roll behavior or a bouncing
behavior. In this case, when driving force or braking force of each
driving wheel is controlled, that is, a driving force allocation is
controlled, to, for example, control the pitch behavior or the roll
behavior while controlling the yaw behavior, control of each of
these behaviors may influence another behavior. Thus, in the case
where the yaw behavior, the pitch behavior and the roll behavior
each are independently controlled, it is difficult to control the
behaviors at the same time only by a simple combination of these
controls, so a favorable ride comfort may not be obtained.
SUMMARY OF THE INVENTION
[0007] The invention provides a vehicle braking/driving force
control system and vehicle braking/driving force control method
that control braking/driving force of each driving wheel to control
a plurality of behaviors of a vehicle body at the same time while
causing the vehicle to run appropriately.
[0008] A first aspect of the invention relates to a vehicle
braking/driving force control system. The vehicle braking/driving
force control system includes a braking/driving force generating
mechanism that causes wheels of a vehicle to respectively generate
driving forces or braking forces independently of one another, and
a suspension mechanism that couples each of the wheels that are not
supported by springs of the vehicle to a vehicle body that is
supported by the springs of the vehicle, and controls the
braking/driving force generating mechanism to cause the wheels to
respectively generate driving forces or braking forces
independently of one another. The vehicle braking/driving force
control system includes: an operating state detecting unit that
detects a driver's operating state for causing the vehicle to run;
a motional state detecting unit that detects a motional state of
the vehicle body while the vehicle is running; a vehicle body
behavior control value computing unit that computes a target
longitudinal driving force for causing the vehicle to run and a
plurality of target motional state amounts for controlling
behaviors of the vehicle body on the basis of the detected
operating state and the detected motional state; and a driving
force allocation computing unit that computes driving forces or
braking forces that are respectively allocated to the wheels so as
to achieve the computed target longitudinal driving force and the
plurality of computed target motional state amounts and that the
braking/driving force generating mechanism causes the wheels to
respectively generate independently of one another.
[0009] In the braking/driving force control system, the driving
force allocation computing unit may compute driving forces or
braking forces that the braking/driving force generating mechanism
causes the wheels to respectively generate independently of one
another on the basis of arrangement of the wheels and suspension
mechanisms of the vehicle using an allocation geometrically
determined so as to achieve the computed target longitudinal
driving force and the plurality of computed target motional state
amounts.
[0010] The braking/driving force control system may further include
a gain computing unit that, when the allocated and computed driving
forces exceeds a maximum driving force of the braking/driving force
generating mechanism or when the allocated and computed braking
forces exceeds a maximum braking force of the braking/driving force
generating mechanism, computes a gain by which driving forces or
braking forces for achieving the plurality of computed target
motional state amounts within the allocated and computed driving
forces or braking forces are reduced.
[0011] In the braking/driving force control system, the gain
computing unit may compute the gain in such a manner that values
obtained by subtracting driving forces for achieving the computed
target longitudinal driving force within the allocated and computed
driving forces from the maximum driving force are divided by the
driving forces for achieving the plurality of target motional state
amounts or values obtained by subtracting braking forces for
achieving the computed target longitudinal driving, force within
the allocated and computed braking forces from the maximum braking
force are divided by the braking forces for achieving the plurality
of target motional state amounts. In addition, in the
braking/driving force control system, the maximum driving force and
the maximum braking force may be determined on the basis of a
ground contact state of the wheels.
[0012] In the braking/driving force control system, the
braking/driving force generating mechanism may include electric
motors that are respectively assembled to the wheels of the
vehicle, and the braking/driving force control system may further
include a torque computing unit that computes driving torques or
braking torques respectively generated by the electric motors in
correspondence with the allocated and computed driving forces or
braking forces. In addition, in the braking/driving force control
system, the braking/driving force generating mechanism may cause
left and right front wheels and left and right rear wheels of the
vehicle to respectively generate driving forces or braking forces
independently of each other, the driving force allocation computing
unit may compute driving forces or braking forces that are
allocated to the left and right front wheels and the left and right
rear wheels in order to achieve the computed target longitudinal
driving force and the plurality of computed target motional state
amounts and that the braking/driving force generating mechanism
causes the left and right front wheels and the left and right rear
wheels to respectively generate independently of each other.
[0013] The braking/driving force control system may further include
an input unit to which the detected operating state and the
detected motional state are input, wherein the vehicle body
behavior control value computing unit may compute a target
longitudinal driving force for causing the vehicle to run and a
plurality of target motional state amounts for controlling
behaviors of the vehicle body on the basis of the operating state
and the motional state that are input by the input unit.
[0014] In the braking/driving force control system, each of the
target motional state amounts may be a target value of any one of a
vertical acceleration in a vertical direction of the vehicle body,
a lateral acceleration in a transverse direction of the vehicle
body, a vehicle speed of the vehicle body, a yaw rate of the
vehicle body, a pitch rate of the vehicle body, a roll rate of the
vehicle body, a yaw moment of the vehicle body, a pitch moment of
the vehicle body and a roll moment of the vehicle body.
[0015] A second aspect of the invention relates to a
braking/driving force control method that, in a vehicle that
includes a braking/driving force generating mechanism that causes
wheels of the vehicle to respectively generate driving forces or
braking forces independently of one another and a suspension
mechanism that couples each of the wheels that are not supported by
springs of the vehicle to a vehicle body that is supported by the
springs of the vehicle, controls the braking/driving force
generating mechanism to cause the wheels to respectively generate
driving forces or braking forces independently of one another. The
braking/driving force control system includes: detecting a driver's
operating state for causing the vehicle to run; detecting a
motional state of the vehicle body while the vehicle is running;
computing a target longitudinal driving force for causing the
vehicle to run and a plurality of target motional state amounts for
controlling behaviors of the vehicle body on the basis of the
detected operating state and the detected motional state; and
computing driving forces or braking forces that are respectively
allocated to the wheels so as to achieve the computed target
longitudinal driving force and the plurality of computed target
motional state amounts and that the braking/driving force
generating mechanism causes the wheels to respectively generate
independently of one another.
[0016] According to the above aspects, the input unit is able to
input the driver's operating state detected by the operating state
detecting unit and the motional state of the vehicle body, detected
by the motional state detecting unit, and the vehicle body behavior
control value computing unit is able to compute the target
longitudinal driving force and the plurality of target motional
state amounts (for example, the target roll moment, the target
pitch moment, the target yaw moment, and the like) on the basis of
at least the detected operating state and motional state. In
addition, the driving force allocation computing unit is able to
compute driving forces or braking forces that are allocated so as
to achieve the target longitudinal driving force and the plurality
of target motional state amounts computed by the vehicle body
behavior control value computing unit at the same time and that the
wheels (more specifically, the left and right front wheels and the
left and right rear wheels) are cause to respectively generate.
Here, when driving forces or braking forces that the wheels (more
specifically, the left and right front wheels and the left and
right rear wheels) are caused to respectively generate are
allocated and computed, it is possible to compute the driving
forces or braking forces on the basis of arrangement of the wheels
and suspension mechanisms of the vehicle using a geometrically
determined allocation. Furthermore, the torque computing unit is
able to compute driving torques or braking torques that are
generated by the braking/driving force generating mechanism
(electric motors) in correspondence with the driving forces or
braking forces that are computed by the driving force allocation
computing unit and that the wheels are caused to respectively
generate.
[0017] By so doing, the braking/driving force generation mechanism
causes the wheels to respectively generate driving forces or
braking forces (driving torques or braking torques). Therefore, it
is possible to appropriately cause the vehicle to run, and it is
possible to control, for example, the roll behavior, pitch behavior
and yaw behavior of the vehicle body at the same time. By so doing,
in comparison with the case where the roll behavior, the pitch
behavior and the yaw behavior are controlled independently of one
another, it is possible to effectively prevent the influence of
controls over the behaviors on one another, and it is possible to
favorably ensure a ride comfort by appropriately causing the
vehicle to run while suppressing a variation in the behaviors of
the vehicle body.
[0018] In addition, when any one of the driving forces or braking
forces computed by the driving force allocation computing unit
exceeds a maximum driving force or a maximum braking force, the
gain computing unit is able to compute a gain by which the driving
forces or braking forces for achieving the plurality of target
motional state amounts computed by the vehicle body behavior
control value computing unit are reduced. In this case,
specifically, the gain computing unit is able to compute the gain
in such a manner that values (behavior control driving forces)
obtained by subtracting driving forces (or braking forces) for
achieving the target longitudinal driving force computed by the
vehicle body behavior control value computing unit within the
driving forces (or braking forces) allocated and computed by the
driving force allocation computing unit from the maximum driving
force (or the maximum braking force) are divided by the driving
forces (or braking forces) for achieving the plurality of target
motional state amounts. Then, in this case, the maximum driving
force and the maximum braking force may be determined on the basis
of the ground contact state of the wheels.
[0019] According to the above aspects, even when any one of the
driving forces or braking forces computed by the driving force
allocation computing unit exceeds the maximum driving force or the
maximum braking force, the plurality of target motional state
amounts (for example, the roll behavior, pitch behavior and yaw
behavior) of the vehicle body may be controlled at the same time
without varying the target longitudinal driving force for causing
the vehicle to run. Thus, it is possible to appropriately control
the behaviors of the vehicle body to thereby make it possible to
ensure a ride comfort, and it is possible to prevent a variation in
vehicle speed (acceleration in the longitudinal direction)
resulting from control over the behaviors of the vehicle body, so
it is possible to effectively prevent the driver from experiencing
a feeling of strangeness. In addition, by determining the maximum
driving force and the maximum braking force on the basis of the
ground contact state of the wheels, it is possible to determine
whether any one of driving forces or braking forces computed by the
driving force allocation computing unit in response to a running
environment of the vehicle exceeds the maximum driving force or the
maximum braking force, and, as a result, it is possible to further
appropriately control the behaviors of the vehicle body.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Features, advantages, and technical and industrial
significance of exemplary embodiments of the invention will be
described below with reference to the accompanying drawings, in
which like numerals denote like elements, and wherein:
[0021] FIG. 1 is a schematic view that schematically shows the
configuration of a vehicle to which a vehicle braking/driving force
control system according to the aspect of the invention may be
applied;
[0022] FIG. 2 is a functional block diagram that functionally shows
computer program processing of braking/driving force control
executed by an electronic control unit shown in FIG. 1 according to
a first embodiment of the invention;
[0023] FIG. 3 is a view for illustrating force input to a vehicle
body when a difference in driving force in a longitudinal direction
occurs in the vehicle shown in FIG. 1; and
[0024] FIG. 4 is a functional block diagram that functionally shows
computer program processing of turning control executed by the
electronic control unit shown in FIG. 1 according to a second
embodiment of the invention.
DETAILED DESCRIPTION OF EMBODIMENTS
a. First Embodiment
[0025] Hereinafter, an embodiment of the invention will be
described in detail with reference to the accompanying drawings.
FIG. 1 schematically shows the configuration of a vehicle Ve
equipped with a vehicle braking/driving force control system
according to embodiments.
[0026] The vehicle Ve includes left and right front wheels 11 and
12 and left and right rear wheels 13 and 14. Then, the left and
right front wheels 11 and 12 are supported by a vehicle body Bo of
the vehicle Ve via respective suspension mechanisms 15 and 16
independently of each other. That is, the vehicle body Bo is
supported by the springs (supported by the suspension mechanisms).
In addition, the left and right rear wheels 13 and 14 are supported
together by the vehicle body Bo of the vehicle Ve via respective
suspension mechanisms 17 and 18. Or the left and right rear wheels
13 and 14 are supported by the vehicle body Bo of the vehicle Ve
via respective suspension mechanisms 17 and 18 independently of
each other.
[0027] Here, the configuration of each of the suspension mechanisms
15 to 18 is not directly linked with the aspect of the invention,
so the detailed description thereof is omitted; however, for
example, a known suspension, such as a strut type suspension formed
of a strut that incorporates a shock absorber, a coil spring, a
suspension arm, and the like, and a wishbone type suspension formed
of a coil spring, a shock absorber, upper and lower suspension
arms, and the like, may be employed.
[0028] Electric motors 19 and 20 are respectively assembled inside
the left and right front wheels 11 and 12. In addition, electric
motors 21 and 22 are respectively assembled inside the left and
right rear wheels 13 and 14. The electric motors 19 and 20 are
respectively coupled to the left and right front wheels 11 and 12
so that power is transmittable. The electric motors 21 and 22 are
respectively coupled to the left and right rear wheels 13 and 14 so
that power is transmittable. That is, the electric motors 19 to 22
are so-called in-wheel motors 19 to 22. The electric motors 19 to
22 together with the left and right front wheels 11 and 12 and the
left and right rear wheels 13 and 14 are not supported by the
springs of the vehicle Ve. Then, by controlling the rotation of
each of the in-wheel motors 19 to 22 independently of one another,
driving forces or braking forces that the left and right front
wheels 11 and 12 and the left and right rear wheels 13 and 14 are
caused to respectively generate may be controlled independently of
one another.
[0029] Each of these in-wheel motors 19 to 22 is, for example,
formed of an alternating-current synchronous motor. Direct-current
electric power from an electrical storage device 24, such as a
battery and a capacitor, is converted to alternating-current
electric power via an inverter 23, and the alternating-current
electric power is supplied to each of the in-wheel motors 19 to 22.
By so doing, each of the in-wheel motors 19 to 22 is driven (that
is, power running), and driving torque is applied to a
corresponding one of the left and right front wheels 11 and 12 and
the left and right rear wheels 13 and 14. In addition, each of the
in-wheel motors 19 to 22 is able to utilize the rotational energy
of a corresponding one of the left and right front wheels 11 and 12
and the left and right rear wheels 13 and 14 to execute
regenerative control. That is, during regeneration or power
generation of each of the in-wheel motors 19 to 22, the rotational
(kinetic) energy of a corresponding one of the left and right front
wheels 11 and 12 and the left and right rear wheels 13 and 14 is
converted to electrical energy by each of the in-wheel motors 19 to
22 and then the generated electric power is stored in the
electrical storage device 24 via the inverter 23. At this time,
braking torque based on regeneration/power generation capacity is
applied to a corresponding one of the left and right front wheels
11 and 12 and the left and right rear wheels 13 and 14. Thus, the
in-wheel motors 19 to 22, the inverter 23 and the electrical
storage device 24 constitute the braking/driving force generating
mechanism according to the aspect of the invention.
[0030] In addition, brake mechanisms 25, 26, 27 and 28 are
respectively provided between the wheels 11 to 14 and the
corresponding in-wheel motors 19 to 22. Each of the brake
mechanisms 25 to 28 is, for example, a known braking device, such
as a disc brake and a drum brake. Then, each of these brake
mechanisms 25 to 28 is, for example, connected to a brake actuator
29. The brake actuator 29 actuates pistons of brake calipers and
brake shoes (both are not shown) that cause the wheels 11 to 14 to
respectively generate braking forces by hydraulic pressure pumped
from a master cylinder (not shown).
[0031] The inverter 23 and the brake actuator 29 each are connected
to an electronic control unit 30. The electronic control unit 30
controls the rotational state of each of the in-wheel motors 19 to
22, the operating state of each of the brake mechanisms 25 to 28,
and the like. Thus, the electronic control unit 30 constitutes the
control unit according to the aspect of the invention.
[0032] The electronic control unit 30 includes a microcomputer
formed of a CPU, a ROM, a RAM, and the like, as major components,
and executes various programs. Therefore, signals from various
sensors and signals from the inverter 23 are input to the
electronic control unit 30. The various sensors include an
operating state detecting sensor 31, a motional state detecting
sensor 32 and a disturbance detecting sensor 33. The operating
state detecting sensor 31 serves as an operating state detecting
unit and detects the driver's operating state for causing the
vehicle Ve to run. The motional state detecting sensor 32 serves as
a motional state detecting unit and detects the motional state of
the vehicle body Bo (sprung mass) arranged on springs, that is, on
suspension mechanisms of the running vehicle Ve. The disturbance
detecting sensor 33 detects a disturbance applied to the running
vehicle Ve.
[0033] Here, the operating state detecting sensor 31 is, for
example, formed of a steering angle sensor, an accelerator sensor,
a throttle sensor, a brake sensor, and the like. The steering angle
sensor detects a driver's operation amount (steering angle) of a
steering wheel (not shown). The accelerator sensor detects a
driver's operation amount (depression amount, angle, pressure, and
the like) of an accelerator pedal (not shown). The throttle sensor
detects the opening degree of a throttle that is provided for an
engine (not shown) and that operates in response to an operation of
the accelerator pedal. The brake sensor detects a driver's
operation amount (depression amount, angle, pressure, and the like)
of a brake pedal (not shown). In addition, the motional state
detecting sensor 32 is, for example, formed of a sprung mass
vertical acceleration sensor, a lateral acceleration sensor, a
vehicle speed sensor, a yaw rate sensor, a pitch rate sensor, a
roll rate sensor, and the like. The sprung mass acceleration sensor
detects the vertical acceleration of the vehicle body Bo (sprung
mass) in the vertical direction. The lateral acceleration sensor
detects the lateral acceleration of the vehicle body Bo in the
transverse direction. The vehicle speed sensor detects the vehicle
speed of the vehicle body Bo (vehicle Ve). The yaw rate sensor
detects the yaw rate of the vehicle body Bo (vehicle Ve). The pitch
rate sensor detects the pitch rate of the vehicle body Bo (vehicle
Ve). The roll rate sensor detects the roll rate of the vehicle body
Bo (vehicle Ve). Furthermore, the disturbance detecting sensor 33
is, for example, formed of a stroke sensor, an unsprung mass
vertical acceleration sensor, and the like. The stroke sensor
detects the stroke amount of each of the suspension mechanisms 15
to 18. The unsprung mass vertical acceleration sensor detects the
vertical acceleration of the unsprung mass, including the wheels 11
to 14, of the vehicle Ve in the vertical direction.
[0034] In this way, because the sensors 31 to 33 and the inverter
23 are connected to the electronic control unit 30 and signals are
input to the electronic control unit 30, the electronic control
unit 30 is able to acquire and control the running condition of the
vehicle Ve and the behaviors of the vehicle body Bo.
[0035] Control over the running condition of the vehicle Ve will be
specifically described first. The electronic control unit 30 is
able to, for example, compute a required driving force
corresponding to an accelerator operation amount when the driver is
operating the accelerator pedal, that is, a driving force that
should be generated by the in-wheel motors 19 to 22 in order to
cause the vehicle Ve to run, on the basis of the signal input from
the operating state detecting sensor 31. In addition, the
electronic control unit 30 is able to, for example, compute a
required braking force corresponding to a brake operation amount
when the driver is operating the brake pedal, that is, a braking
force that should be generated by coordination between the in-wheel
motors 19 to 22 and the brake mechanisms 25 to 28 in order to
decelerate the vehicle Ve, on the basis of the signal input from
the operating state detecting sensor 31. Then, the electronic
control unit 30 causes the in-wheel motors 19 to 22 to generate an
output torque (motor torque) corresponding to the required driving
force or causes the in-wheel motors 19 to 22 to generate an output
torque (motor torque) corresponding to the required braking force
on the basis of the signal input from the inverter 23,
specifically, signals that indicate the amounts of electric power
and current values respectively supplied to the in-wheel motors 19
to 22 during power running control or signals that indicate the
amounts of electric power and current values respectively
regenerated from the in-wheel motors 19 to 22 during regenerative
control.
[0036] By so doing, the electronic control unit 30 is able to
output signals for executing power running control or regenerative
control over the rotations of the in-wheel motors 19 to 22 via the
inverter 23 and to output signals for controlling the operations of
the brake mechanisms 25 to 28 via the brake actuator 29. Thus, the
electronic control unit 30 at least obtains a required driving
force or a required braking force required of the vehicle Ve on the
basis of the signal input from the operating state detecting sensor
31, and then outputs signals for controlling the power
running/regenerative states of the in-wheel motors 19 to 22 and the
operations of the brake actuator 29, that is, the brake mechanisms
25 to 28, so as to generate the required driving force or the
required braking force to thereby make it possible to control the
running condition of the vehicle Ve.
[0037] On the other hand, the electronic control unit 30 is able to
control the behaviors of the vehicle body Bo (sprung mass) on the
basis of the signals input from the operating state detecting
sensor 31, the motional state detecting sensor 32 and the
disturbance detecting sensor 33. Hereinafter, control over the
behaviors of the vehicle body Bo will be described in detail.
[0038] The electronic control unit 30 according to the first
embodiment appropriately controls the allocation of driving forces
(or braking forces) that the in-wheel motors 19 to 22 respectively
generate to thereby cause the vehicle Ve to run, and controls the
roll behavior, the pitch behavior and the yaw behavior as the
behaviors of the vehicle body Bo (sprung mass). Therefore, as shown
in FIG. 2, the electronic control unit 30 includes an input unit
41, a vehicle body behavior control command value computing unit
42, a driving force allocation computing unit 43, a wheel motor
torque command value computing unit 44 and an output unit 45. The
vehicle body behavior control command value computing unit 42
serves as a vehicle body behavior control value computing unit. The
wheel motor torque command value computing unit 44 serves as a
torque computing unit.
[0039] Signals are input from the operating state detecting sensor
31, the motional state detecting sensor 32 and the disturbance
detecting sensor 33 to the input unit 41. Then, the input unit 41,
for example, acquires the steering angle of the steering wheel
operated by the driver, the accelerator operation amount and the
throttle opening degree resulting from an operation of the
accelerator pedal, the brake operation amount resulting from an
operation of the brake pedal, and the like, on the basis of the
signal input from the operating state detecting sensor 31. In
addition, the input unit 41, for example, acquires the vehicle
speed of the vehicle body Bo (vehicle Ve), the roll rate, pitch
rate and yaw rate of the vehicle body Bo, and the like, on the
basis of the signal input from the motional state detecting sensor
32. Furthermore, the input unit 41, for example, acquires the
degree of unevenness of a road surface on which the vehicle Ve is
running, the degree of influence of cross wind on the vehicle Ve,
and the like, on the basis of the signal input from the disturbance
detecting sensor 33. In this way, when the input unit 41 acquires
various detected values, the input unit 41 outputs the acquired
various detected values to the vehicle body behavior control
command value computing unit 42.
[0040] The vehicle body behavior control command value computing
unit 42 uses the various detected values input from the input unit
41 to compute a target longitudinal driving force F.sub.X as a
control command value for causing the vehicle Ve to run, and
computes control command values for controlling the behaviors of
the vehicle body Bo, that is, a target roll moment M.sub.x, a
target pitch moment M.sub.y and a target yaw moment M.sub.z as a
plurality of target motional state amounts. Note that a known
computing method may be employed to compute the target longitudinal
driving force F.sub.X, the target roll moment M.sub.x, the target
pitch moment M.sub.y and the target yaw moment M.sub.z, so the
described description thereof is omitted; however, the computation
will be simply described below.
[0041] First, for the target longitudinal driving force F.sub.X
that the in-wheel motors 19 to 22 generate to cause the vehicle Ve
to run, the vehicle body behavior control command value computing
unit 42, for example, uses detected values, such as the accelerator
operation amount, the throttle opening degree, the brake operation
amount and the vehicle speed, input from the input unit 41, to
compute the target longitudinal driving force F.sub.X that is in a
predetermined correlation with these detected values. For the
target roll moment M.sub.x, the vehicle body behavior control
command value computing unit 42, for example, uses the detected
values, such as the steering angle, the vehicle speed, the roll
rate, the degree of unevenness of a road surface and the degree of
influence of cross wind, input from the input unit 41, to compute
the target roll moment M.sub.x that is in a predetermined
correlation with these detected values. For the target pitch moment
M.sub.y, the vehicle body behavior control command value computing
unit 42, for example, uses the detected values, such as the
accelerator operation amount, the throttle opening degree, the
brake operation amount, the vehicle speed, the pitch rate and the
degree of unevenness of a road surface, input from the input unit
41, to compute the target pitch moment M.sub.y that is in a
predetermined correlation with these detected values. For the
target yaw moment M.sub.z, the vehicle body behavior control
command value computing unit 42, for example, uses the detected
values, such as the steering angle, the vehicle speed, the yaw rate
and the degree of influence of cross wind, input from the input
unit 41, to compute the target yaw moment M.sub.z that is in a
predetermined correlation with these detected values.
[0042] In this way, when the vehicle body behavior control command
value computing unit 42 computes the target longitudinal driving
force F.sub.X, the target roll moment M.sub.x, the target pitch
moment M.sub.y and the target yaw moment M.sub.z, the vehicle body
behavior control command value computing unit 42 outputs command
values that respectively indicate the computed target longitudinal
driving force F.sub.X, target roll moment M.sub.x, target pitch
moment M.sub.y and target yaw moment M.sub.z to the driving force
allocation computing unit 43.
[0043] The driving force allocation computing unit 43 computes
driving forces that are respectively allocated to and generated by
the wheels 11 to 14 in order to generate the target longitudinal
driving force F.sub.X indicated by the command value output from
the vehicle body behavior control command value computing unit 42.
In addition, the driving force allocation computing unit 43
computes driving forces that are respectively allocated to and
generated by the wheels 11 to 14 in order to generate the target
roll moment M.sub.x, target pitch moment M.sub.y and target yaw
moment M.sub.z, indicated by the command values output from the
vehicle body behavior control command value computing unit 42, at
the position of the barycenter of the vehicle Ve. That is, the
driving force allocation computing unit 43 computes a front left
driving force F.sub.fl for the left front wheel 11, a front right
driving force F.sub.fr for the right front wheel 12, a rear left
driving force F.sub.rl for the left rear wheel 13 and a rear right
driving force F.sub.rr for the right rear wheel 14 in accordance
with the following mathematical expression (1) that uses the target
longitudinal driving force F.sub.X, the target roll moment M.sub.x,
the target pitch moment M.sub.y and the target yaw moment
M.sub.z.
[ Mathematical Expression ( 1 ) ] [ F fl F fr F rl F rr ] = [ 1 1 1
1 - a 1 a 1 a 2 - a 2 a 3 a 3 a 4 a 4 - a 5 a 5 - a 6 a 6 ] - 1 [ F
X M x M y M z ] ( 1 ) ##EQU00001##
In the mathematical expression (1), a.sub.1, a.sub.2, a.sub.3,
a.sub.4, a.sub.5 and a.sub.6 are determined on the basis of the
geometrical arrangement of the wheels 11 to 14 and suspension
mechanisms 15 to 18 of the vehicle Ve, and are expressed by the
following mathematical expression (2).
[ Mathematical Expression ( 2 ) ] a 1 = t f 2 tan .theta. f , a 2 =
t r 2 tan .theta. r , a 3 = L f tan .theta. f , a 4 = L r tan
.theta. r , a 5 = t f 2 , a 6 = t r 2 ( 2 ) ##EQU00002##
[0044] Here, the mathematical expression (1) and the mathematical
expression (2) will be specifically described with reference to
FIG. 1 and FIG. 3. Now, as is schematically shown in FIG. 3, as the
geometrical arrangement of the wheels 11 to 14 and suspension
mechanisms 15 to 18 of the vehicle Ve, the distance between the
barycenter Cg of the vehicle Ve and the axles of the left and right
front wheels 11 and 12 is denoted by L.sub.f and the distance
between the barycenter Cg of the vehicle Ve and the axles of the
left and right rear wheels 13 and 14 is denoted by L.sub.r with
respect to a wheel base L, and, as shown in FIG. 1, the tread width
between the left and right front wheels 11 and 12 is denoted by
t.sub.f and the tread width between the left and right rear wheels
13 and 14 is denoted by t.sub.r. In addition, in the vehicle Ve
having such geometrical arrangement, the angle between the
horizontal line and the line that connects the rotation center Cf
of each of the suspension mechanisms 15 and 16 of the left and
right front wheels 11 and 12 to the ground contact point of each of
the left and right front wheels 11 and 12 is denoted by
.theta..sub.f (hereinafter, referred to as instantaneous rotation
angle .theta..sub.f), and the angle between the horizontal line and
the line that connects the rotation center Cr of each of the
suspension mechanisms 17 and 18 of the left and right rear wheels
13 and 14 to the ground contact point of each of the left and right
front wheels 13 and 14 is denoted by .theta..sub.r (hereinafter,
referred to as instantaneous rotation angle .theta..sub.r).
[0045] In this case, for example, as shown in FIG. 3, when there
occurs a driving force difference .DELTA.F in the longitudinal
direction between the left and right front wheels 11 and 12 and the
left and right rear wheels 13 and 14, there occur vertical forces
that act in the vertical direction as the component forces of the
driving force difference .DELTA.F, that is, the reaction forces of
the suspension mechanisms 15 to 18. Note that FIG. 3, for example,
shows the case where driving forces that the left and right rear
wheels 13 and 14 respectively generate are larger than driving
forces that the left and right front wheels 11 and 12 respectively
generate, and shows a situation that, as a result, the driving
force difference .DELTA.F that occurs in the left and right front
wheels 11 and 12 relatively occurs as a braking force that acts on
the rear of the vehicle Ve, and the driving force difference
.DELTA.F that occurs in the left and right rear wheels 13 and 14
relatively occurs as a driving force that acts on the front of the
vehicle Ve. Thus, on the contrary, when driving forces that the
left and right front wheels 11 and 12 respectively generate are
larger than driving forces that the left and right rear wheels 13
and 14 respectively generate, the driving force difference .DELTA.F
that occurs in the left and right front wheels 11 and 12 relatively
occurs as a driving force that acts on the rear of the vehicle Ve,
and the driving force difference .DELTA.F that occurs in the left
and right rear wheels 13 and 14 relatively occurs as a braking
force that acts on the front of the vehicle Ve.
[0046] Then, the vertical force that occurs in this way may be
expressed by .DELTA.Fxtan.theta..sub.f using the instantaneous
rotation angle .theta..sub.f of each of the suspension mechanisms
15 and 16 for the left and right front wheels 11 and 12, and may be
expressed by .DELTA.Fxtan.theta..sub.r using the instantaneous
rotation angle .theta..sub.r of each of the suspension mechanisms
17 and 18 for the left and right rear wheels 13 and 14. Thus, when
the driving force difference .DELTA.F is generated in each of the
wheels 11 to 14 in this way and then the vertical forces
.DELTA.Fxtan.theta..sub.f and the vertical forces
.DELTA.Fxtan.theta..sub.r that are input to the vehicle body Bo are
caused to act around the barycenter Cg of the vehicle Ve, acting
force generated around the barycenter Cg is geometrically
determined on the basis of the above described arrangement of the
wheels 11 to 14 and suspension mechanisms 15 to 18 of the vehicle
Ve in accordance with the mathematical expression (2).
[0047] Then, by using the acting force determined in accordance
with the mathematical expression (2) based on the geometrical
arrangement in this way, the computed target roll moment M.sub.x,
target pitch moment M.sub.y and target yaw moment M.sub.z may be
generated around the barycenter Cg of the vehicle Ve with respect
to the vehicle body Bo. Thus, by computing the front left driving
force F.sub.fl for the left front wheel 11, the front right driving
force F.sub.fr for the right front wheel 12, the rear left driving
force F.sub.rl for the left rear wheel 13 and the rear right
driving force F.sub.rr for the right rear wheel 14 on the basis of
the mathematical expression (1) and the mathematical expression
(2), the computed target roll moment M.sub.x, target pitch moment
M.sub.y and target yaw moment M.sub.z may be generated around the
barycenter Cg at the same time to thereby control the behaviors of
the vehicle body Bo. In this way, when the front left driving force
F.sub.fl for the left front wheel 11, the front right driving force
F.sub.fr for the right front wheel 12, the rear left driving force
F.sub.rl for the left rear wheel 13 and the rear right driving
force F.sub.rr for the right rear wheel 14 are computed in
accordance with the mathematical expression (1) and the
mathematical expression (2), the driving force allocation computing
unit 43 outputs the front left driving force F.sub.fl, the front
right driving force F.sub.fr, the rear left driving force F.sub.rl
and the rear right driving force F.sub.rr to the wheel motor torque
command value computing unit 44.
[0048] The wheel motor torque command value computing unit 44
computes motor torques that should be respectively generated by the
in-wheel motors 19 to 22 in correspondence with the front left
driving force F.sub.fl, front right driving force F.sub.fr, rear
left driving force F.sub.rl and rear right driving force F.sub.rr
computed by the driving force allocation computing unit 43. That
is, the wheel motor torque command value computing unit 44 computes
a motor torque T.sub.fl that the in-wheel motor 19 generates in
correspondence with the front left driving force F.sub.fl, a motor
torque T.sub.fr that the in-wheel motor 20 generates in
correspondence with the front right driving force F.sub.fr, a motor
torque T.sub.rl that the in-wheel motor 21 generates in
correspondence with the rear left driving force F.sub.rl and a
motor torque T.sub.rr that the in-wheel motor 22 generates in
correspondence with the rear left driving force F.sub.rr in
accordance with the following mathematical expression (3).
[ Mathematical Expression 3 ] [ T fl T fr T rl T rr ] = r [ 1 1 1 1
- a 1 a 1 a 2 - a 2 a 3 a 3 a 4 a 4 - a 5 a 5 - a 6 a 6 ] - 1 [ F X
M x M y M z ] ( 3 ) ##EQU00003##
In the mathematical expression (3), r denotes the tire radius (or
the gear ratio of the reduction mechanism (not shown)) of each of
the wheels 11 to 14 as shown in FIG. 3. Then, the wheel motor
torque command value computing unit 44 outputs the computed motor
torques T.sub.fl, T.sub.fr, T.sub.rl and T.sub.rr to the output
unit 45.
[0049] The output unit 45 outputs driving signals corresponding to
the motor torques T.sub.fl, T.sub.fr, T.sub.rl and T.sub.rr
computed by the wheel motor torque command value computing unit 44
to the inverter 23. By so doing, the inverter 23 controls driving
electric powers (driving currents) supplied respectively to the
in-wheel motors 19 to 22 to drive the in-wheel motors 19 to 22. By
so doing, the front left driving force F.sub.fl, front right
driving force F.sub.fr, rear left driving force F.sub.rl and rear
right driving force F.sub.rr computed by the driving force
allocation computing unit 43 are respectively generated by the
wheels 11 to 14. As a result, the vehicle Ve may be appropriately
caused to run in response to a driver's operating state, and the
behaviors of the vehicle body Bo, that is, the roll behavior, the
pitch behavior and the yaw behavior, may be controlled at the same
time.
[0050] As can be understood from the above description, according
to the first embodiment, the vehicle body behavior control command
value computing unit 42 is able to compute the target longitudinal
driving force F.sub.X, the target roll moment M.sub.x, the target
pitch moment M.sub.y and the target yaw moment M.sub.z on the basis
of various detected values input from the input unit 41. In
addition, the driving force allocation computing unit 43 computes
driving forces that the wheels 11 to 14 are caused to respectively
generate, specifically, the front left driving force F.sub.fl, the
front right driving force F.sub.fr, the rear left driving force
F.sub.rl and the rear right driving force F.sub.rr, so as to
achieve the target longitudinal driving force F.sub.X, the target
roll moment M.sub.x, the target pitch moment M.sub.y and the target
yaw moment M.sub.z at the same time. The wheel motor torque command
value computing unit 44 is able to compute motor torques T.sub.fl,
T.sub.fr, T.sub.rl and T.sub.rr to be generated by the in-wheel
motors 19 to 22 provided for the wheels 11 to 14 in correspondence
with the front left driving force F.sub.fl, the front right driving
force F.sub.fr, the rear left driving force F.sub.rl and the rear
right driving force F.sub.rr.
[0051] Then, the in-wheel motors 19 to 22 respectively generate the
motor torques T.sub.fl, T.sub.fr, T.sub.rl and T.sub.rr
corresponding to the front left driving force F.sub.fl, the front
right driving force F.sub.fr, the rear left driving force F.sub.rl
and the rear right driving force F.sub.rr. By so doing, it is
possible to appropriately cause the vehicle Ve to run and to
control the roll behavior, pitch behavior and yaw behavior of the
vehicle body Bo at the same time. By so doing, in comparison with
the case where the roll behavior, the pitch behavior and the yaw
behavior are controlled independently of one another, it is
possible to effectively prevent the influence of controls over the
behaviors on one another, and it is possible to favorably ensure a
ride comfort while suppressing a variation in the behaviors of the
vehicle body Bo.
b. Second Embodiment
[0052] Next, a second embodiment of the invention will be
described. In the first embodiment, in order to generate the target
longitudinal driving force F.sub.X, target roll moment M.sub.x,
target pitch moment M.sub.y and target yaw moment M.sub.z computed
by the vehicle body behavior control command value computing unit
42, the driving force allocation computing unit 43 computes the
front left driving force F.sub.fl, the front right driving force
F.sub.fr, the rear left driving force F.sub.rl and the rear right
driving force F.sub.rr, and the wheel motor torque command value
computing unit 44 computes the motor torques T.sub.fl, T.sub.fr,
T.sub.rl and T.sub.rr. Then, in the first embodiment, the in-wheel
motors 19 to 22 respectively generate the computed motor torques
T.sub.fl, T.sub.fr, T.sub.rl and T.sub.rr.
[0053] In this case, when a plurality of behaviors of the vehicle
body Bo are controlled, for example, a driving force (or a braking
force) in any one of the wheels 11 to 14, that is, a motor torque
required of any one of the in-wheel motors 19 to 22, may exceed a
preset upper limit of generatable torque or may exceed a ground
contact state of the wheels 11 to 14, specifically, a limit made by
a tire friction circle, or the like. In this case, when the entire
driving force (motor torque) is simply limited by a percentage at
which a driving force (or a braking force) that should be generated
or a required motor torque exceeds the above described upper limit
or limit, for example, it may be difficult to keep (control) the
vehicle speed because of a variation in the longitudinal
acceleration of the vehicle Ve. Therefore, in the second
embodiment, without varying components associated with the target
longitudinal driving force F.sub.X for appropriately causing the
vehicle Ve to run within the front left driving force F.sub.fl,
front right driving force F.sub.fr, rear left driving force
F.sub.rl and rear right driving force F.sub.rr computed by the
driving force allocation computing unit 43 (that is, without
varying the target longitudinal driving force F.sub.X), only
components associated with the target roll moment M.sub.x, the
target pitch moment M.sub.y and the target yaw moment M.sub.z for
controlling a plurality of behaviors of the vehicle body Bo are
reduced. Hereinafter, the second embodiment will be described in
detail; however, like reference numerals denote similar components
to those of the first embodiment, and the description thereof is
omitted.
[0054] The second embodiment shown in FIG. 4 differs from the first
embodiment shown in FIG. 2 in that a gain computing unit 46 is
provided. When any one of the front left driving force F.sub.fl,
front right driving force F.sub.fr, rear left driving force
F.sub.rl and rear right driving force F.sub.rr computed by the
driving force allocation computing unit 43 exceeds a driving force
F.sub.limit that is a maximum driving force (or maximum braking
force) that each of the in-wheel motors 19 to 22 is able to
generate in a corresponding one of the wheels 11 to 14, the gain
computing unit 46 computes a gain K by which the components of the
front left driving force F.sub.fl, front right driving force
F.sub.fr, rear left driving force F.sub.rl and rear right driving
force F.sub.rr associated with the target roll moment M.sub.x,
target pitch moment M.sub.y and target yaw moment M.sub.z computed
by the vehicle body behavior control command value computing unit
42 are reduced. Hereinafter, the gain computing unit 46 will be
described in detail.
[0055] As described above, the gain computing unit 46 computes and
determines a gain K in such a manner that only components
associated with control over the target roll moment M.sub.x, the
target pitch moment M.sub.y and the target yaw moment M.sub.z
within the components of the front left driving force F.sub.fl,
front right driving force F.sub.fr, rear left driving force
F.sub.rl and rear right driving force F.sub.rr computed by the
driving force allocation computing unit 43 are reduced without
varying the target longitudinal driving force F.sub.X. Here, as is
apparent from the mathematical expression (1), the target
longitudinal driving force F.sub.X is the resultant force of the
front left driving force F.sub.fl, the front right driving force
F.sub.fr, the rear left driving force F.sub.rl and the rear right
driving force F.sub.rl generated by the wheels 11 to 14, so, for
the sake of convenience, an average driving force F.sub.Xi per one
wheel may be F.sub.X/4 that is obtained by dividing the target
longitudinal driving force F.sub.X by 4.
[0056] Thus, the driving force of each of the wheels 11 to 14,
which may be used in control over the target roll moment M.sub.x,
the target pitch moment M.sub.y and the target yaw moment M.sub.z
of the vehicle body Bo without varying the target longitudinal
driving force F.sub.X, is a force obtained by subtracting the
average driving force F.sub.Xi from the driving force (hereinafter,
referred to as behavior control driving force
(F.sub.limit-F.sub.Xi)) at the maximum. Here, as shown in FIG. 4,
the gain computing unit 46 is able to input a signal from the
inverter 23, to determine one of the in-wheel motors 19 to 22,
which is currently generating the maximum driving force, and to
acquire, from the driving force allocation computing unit 43, a
driving force F.sub.c that the determined one of the in-wheel
motors is generating in order to control the target roll moment
M.sub.x, the target pitch moment M.sub.y and the target yaw moment
M.sub.z.
[0057] Then, when a value obtained by dividing the behavior control
driving force (F.sub.limit-F.sub.Xi) by the driving force F.sub.c
is larger than or equal to "1", the driving force F.sub.c that the
determined one of the in-wheel motors is generating is smaller than
the behavior control driving force (F.sub.limit-F.sub.Xi), that is,
the driving force F.sub.c may be generated with an allowance, so
the gain computing unit 46 does not compute the gain K (or sets the
gain K at "1"). On the other hand, when a value obtained by
dividing the behavior control driving force (F.sub.limit-F.sub.Xi)
by the driving force F.sub.c is smaller than "1", the driving force
F.sub.c that the determined one of the in-wheel motors is
generating is larger than the behavior control driving force
(F.sub.limit-F.sub.Xi), that is, the driving force F.sub.c may not
be generated appropriately. Therefore, the gain computing unit 46
computes the gain K in accordance with the mathematical expression
(4) or the mathematical expression (5) in response to the direction
of the driving force F.sub.c that the determined one of the
in-wheel motors is generating, that is, whether the driving force
F.sub.c is a driving force that propels the vehicle Ve forward or a
braking force that brakes the vehicle Ve.
[ Mathematical Expression 4 ] K = ( F limit - F Xi ) F c ( F c >
0 ) ( 4 ) [ Mathematical Expression 5 ] K = ( - F limit - F Xi ) F
c ( F c < 0 ) ( 5 ) ##EQU00004##
Here, the driving force F.sub.limit in the mathematical expression
(4) corresponds to the maximum driving force, and the driving force
-F.sub.limit in the mathematical expression (5) corresponds to the
maximum braking force.
[0058] In this way, when the gain K is computed and determined in
accordance with the mathematical expression (4) or the mathematical
expression (5), the gain computing unit 46 multiplies the target
roll moment M.sub.x, target pitch moment M.sub.y and target yaw
moment M.sub.z, computed by the vehicle body behavior control
command value computing unit 42, by the determined gain K. Then,
the gain computing unit 46 outputs the target longitudinal driving
force F.sub.X computed by the vehicle body behavior control command
value computing unit 42 and the target roll moment M.sub.x, target
pitch moment M.sub.y and target yaw moment M.sub.z that are
multiplied by the gain K to the driving force allocation computing
unit 43.
[0059] The driving force allocation computing unit 43 computes
driving forces that are respectively allocated to and that should
be respectively generated by the wheels 11 to 14 in order to
generate the target longitudinal driving force F.sub.X indicated by
the command value output from the vehicle body behavior control
command value computing unit 42 via the gain computing unit 46. In
addition, the driving force allocation computing unit 43 computes
driving forces that are respectively allocated to and that should
be respectively generated by the wheels 11 to 14 in order to
generate the target roll moment KM.sub.x, target pitch moment
KM.sub.y and target yaw moment KM.sub.z, indicated by the command
values output from the gain computing unit 46, around the
barycenter Cg of the vehicle Ve. That is, the driving force
allocation computing unit 43 computes a front left driving force
F.sub.fl for the left front wheel 11, a front right driving force
F.sub.fr for the right front wheel 12, a rear left driving force
F.sub.rl for the left rear wheel 13 and a rear right driving force
F.sub.rr for the right rear wheel 14 in accordance with the
following mathematical expression (6) that uses the target
longitudinal driving force F.sub.X, the target roll moment
KM.sub.x, the target pitch moment KM.sub.y and the target yaw
moment KM.sub.z. By so doing, the driving force allocation
computing unit 43 is able to reduce only components associated with
control over the target roll moment M.sub.x, the target pitch
moment M.sub.y and the target yaw moment M.sub.z within the
components of the front left driving force F.sub.fl, the front
right driving force F.sub.fr, the rear left driving force F.sub.rl
and the rear right driving force F.sub.rr using the gain K.
[ Mathematical Expression 6 ] [ F fl F fr F rl F rr ] = [ 1 1 1 1 -
a 1 a 1 a 2 - a 2 a 3 a 3 a 4 a 4 - a 5 a 5 - a 6 a 6 ] - 1 [ F X K
M x K M y K M z ] ( 6 ) ##EQU00005##
[0060] In this way, when the front left driving force F.sub.fl for
the left front wheel 11, the front right driving force F.sub.fr for
the right front wheel 12, the rear left driving force F.sub.rl for
the left rear wheel 13 and the rear right driving force F.sub.rr
for the right rear wheel 14 are computed in accordance with the
mathematical expression (6), the driving force allocation computing
unit 43 outputs the front left driving force F.sub.fl, the front
right driving force F.sub.fr, the rear left driving force F.sub.rl
and the rear right driving force F.sub.rr to the wheel motor torque
command value computing unit 44. As in the case of the first
embodiment, the wheel motor torque command value computing unit 44
computes a motor torque T.sub.fl that the in-wheel motor 19
generates in correspondence with the front left driving force
F.sub.fl, a motor torque T.sub.fr that the in-wheel motor 20
generates in correspondence with the front right driving force
F.sub.fr, a motor torque T.sub.rl that the in-wheel motor 21
generates in correspondence with the rear left driving force
F.sub.rl and a motor torque T.sub.rr that the in-wheel motor 22
generates in correspondence with the rear left driving force
F.sub.rr in accordance with the following mathematical expression
(7).
[ Mathematical Expression 7 ] [ T fl T fr T rl T rr ] = r [ 1 1 1 1
- a 1 a 1 a 2 - a 2 a 3 a 3 a 4 a 4 - a 5 a 5 - a 6 a 6 ] - 1 [ F X
K M x K M y K M z ] ( 7 ) ##EQU00006##
[0061] As in the case of the first embodiment, the output unit 45
outputs driving signals corresponding to the motor torques
T.sub.fl, T.sub.fr, T.sub.rl and T.sub.rr computed by the wheel
motor torque command value computing unit 44 to the inverter 23. By
so doing, the inverter 23 controls driving electric powers (driving
currents) supplied respectively to the in-wheel motors 19 to 22 to
drive the in-wheel motors 19 to 22. By so doing, the front left
driving force F.sub.fl, front right driving force F.sub.fr, rear
left driving force F.sub.rl and rear right driving force F.sub.rr
computed by the driving force allocation computing unit 43 are
respectively generated by the wheels 11 to 14, and, as a result,
the behaviors of the vehicle body Bo, that is, the roll behavior,
the pitch behavior and the yaw behavior, may be controlled at the
same time without varying the target longitudinal driving force
F.sub.X.
[0062] As can be understood from the above description, according
to the second embodiment, when any one of the front left driving
force F.sub.fl, the front right driving force F.sub.fr, the rear
left driving force F.sub.rl and the rear right driving force
F.sub.rr computed by the driving force allocation computing unit 43
exceeds the driving force F.sub.limit, the gain computing unit 46
is able to compute and determine a gain K. Then, the driving force
allocation computing unit 43 is able to compute the front left
driving force F.sub.fl, the front right driving force F.sub.fr, the
rear left driving force F.sub.rl and the rear right driving force
F.sub.rr for achieving the target roll moment KM.sub.x, the target
pitch moment KM.sub.y and the target yaw moment KM.sub.z that are
obtained by applying the gain K computed by the gain computing unit
46 to the target roll moment M.sub.x, target pitch moment M.sub.y
and target yaw moment M.sub.z computed by the vehicle body behavior
control command value computing unit 42.
[0063] By so doing, even when any one of the front left driving
force F.sub.fl, front right driving force F.sub.fr, rear left
driving force F.sub.rl and rear right driving force F.sub.rr
computed by the driving force allocation computing unit 43 exceeds
the driving force F.sub.limit, the roll behavior, pitch behavior
and yaw behavior of the vehicle body Bo may be controlled at the
same time without varying the target longitudinal driving force
F.sub.X for causing the vehicle Ve to run. Thus, in the second
embodiment as well, as in the case of the first embodiment, it is
possible to appropriately control the behaviors of the vehicle body
Bo to thereby make it possible to ensure a ride comfort, and it is
possible to prevent a variation in vehicle speed (acceleration in
the longitudinal direction) resulting from control over the
behaviors of the vehicle body Bo, so it is possible to effectively
prevent the driver from experiencing a feeling of strangeness.
[0064] The aspect of the invention is not limited to the above
described embodiments; it may be modified in various forms without
departing from the scope of the invention.
[0065] For example, in the above embodiments, the front left
driving force F.sub.fl, front right driving force F.sub.fr, rear
left driving force F.sub.rl and rear right driving force F.sub.rr
computed by the driving force allocation computing unit 43 are
controlled independently of one another. In this case, driving
forces (or braking forces) that the left and right front wheels 11
and 12 respectively generate and driving forces (or braking forces)
that the left and right rear wheels 13 and 14 respectively generate
may be opposite and their absolute values may be equal to each
other so as not to influence the longitudinal motion of the vehicle
Ve, that is, so as not to generate the acceleration or deceleration
in the vehicle Ve. By so doing, a driving force difference (or a
braking force difference) that occurs in the left and right front
wheels 11 and 12 and a driving force difference (or a braking force
difference) that occurs in the left and right rear wheels 13 and 14
cancel each other, so it is possible to effectively prevent a
reduction in longitudinal driving force required to cause the
vehicle Ve to run, and advantageous effects similar to those of the
above described embodiments may be obtained.
[0066] In addition, in the above described embodiments, the driving
force allocation computing unit 43 computes the front left driving
force F.sub.fl, the front right driving force F.sub.fr, the rear
left driving force F.sub.rl and the rear right driving force
F.sub.rr. In this case, for example, the driving force allocation
computing unit 43 may be configured to compute a front wheel-side
driving force to be generated by cooperation between the left and
right front wheels 11 and 12 and a rear wheel-side driving force to
be generated by cooperation between the left and right rear wheels
13 and 14. By so doing as well, advantageous effects similar to
those of the above described embodiments may be obtained.
* * * * *